Unlike most border states most Texas border land private owned.
https://www.washingtonpost.com/graphics/national/challenges-building-border-wall/
For the border in the middle of the Rio Grande
Sub contract it to the ChiComs
They adept at building down rivers.
Install floating barriers between the columns
And since the gobmint is in bed with Elon Musk....have all the border guards issued with the handy dandy E-M high tech flame thrower